<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>三目运算符</title>
  <script>
  </script>
</head>

<body>
  <button onclick="myBtnAction()">
    改变flag
  </button>
</body>
<script>
  var flag = true;

  function myBtnAction() {
    flag = !flag;
    var a = flag ? "✅" : "❌"
    console.log(a);
  }
</script>

</html>